This invention relates generally to optical ring networks and more particularly to a method of deactivating protection fiber resources in optical ring networks.
Today""s optical transport networks employ a number of different topologies to satisfy increasing demands for network simplicity, cost containment, bandwidth efficiency and protection. Common network topologies include point-to-point terminal configurations, linear add/drop multiplexer configurations and ring configurations. Of all these different topologies, ring configurations are often the preferred network configuration for applications requiring high transport capacity.
In optical ring networks, the bandwidth available in each fiber interconnecting nodes can be allocated in various ways to meet different capacity demands. In some ring configurations, the bandwidth available for transport can be provisioned as a single optical transmission path. However, in the vast majority of ring configurations, the bandwidth is partitioned into channels or wavelengths to increase capacity.
In optical ring networks as in other optical configurations, it is common to use the term fiber generally to denote traffic carrying capacity. As such, in addition to denote physical fibers, the term fiber can also be used to denote single channels or wavelengths in a physical fiber. For clarity and unless stated otherwise, the term fiber as applied generally to optical networks is hereinafter used to denote both a physical fiber and a single channel or wavelength within a physical fiber.
In addition to providing large capacity, optical ring systems are also designed with redundant equipment to have other attributes such as, for example, bidirectionality and/or increased reliability to reduce service failures. In conventional unidirectional and bidirectional ring systems for example, multiple fibers are commonly installed to achieve transmit and receive operations. Additional fibers are also installed to xe2x80x9cprotectxe2x80x9d the working fibers in the event of a link (span) failure. Current ring protection schemes include dedicated protection, 1 protection fiber for each fiber or 1:1 protection which can be used in both path switched and line switched configurations.
Because of the protection requirements that are necessary in a ring configuration, all spans in a ring are provisioned with at least one protection path. However, for some ring configurations, this requirement can lead to inefficiencies. In interconnected ring configurations for example, the interconnected rings must have distinct protection capabilities with at least one dedicated protection path for each span of each ring. On spans with interconnecting nodes common to two or more rings, this means that distinct protection paths must be provisioned which therefore necessitates dedicated protection fibers or channels for each ring. In applications with rapidly growing demands for ring interconnectivity, this protection usage is inefficient and can lead to considerable capital outlays, particularly on spans where a large number of rings must be accommodated.
In addition to this ineffective use of protection fibers or channels, the protection of multiple rings between nodes necessitates replicating some of the connection equipment required at each node. In interconnected ring systems such as described above, this would require duplicating some of the optics apparatus for each protection fiber or channel provisioned. Duplicating this equipment for each protection fiber/channel may also prove to have a considerable impact on the system cost.
Therefore, it would be desirable to use the existing protection capabilities more efficiently in interconnected ring configurations or alternatively deactivate redundant protection fiber resources so that they can be removed or re-provisioned for use in other network configurations.
The present invention consists of a method of deactivating protection fiber resources in an existing optical network having interconnected rings. The invention can be used in any optical network or system with a separate path for protected traffic whether it is a physical fiber or wavelength to deactivate protection resources between nodes common to two or more optical rings. This may include for example bidirectional line switched ring (BLSR) configurations.
According to a broad aspect, the invention can be applied to deactivate physical working fibers as well as working channels or wavelengths provisioned on a physical working fiber. For clarity, the term fiber is hereinafter used to denote both a physical fiber and a channel or wavelength provisioned on a physical fiber.
In a preferred embodiment, the invention is incorporated in a BLSR network formed of a series of interconnected optical rings to deactivate protection fibers or channels between nodes common to two or more optical rings. According to the preferred embodiment, a common protection path is defined between each pair of common nodes whereby only one protection fiber or channel is used to provide protection for two or more optical rings supported there between. As a result, any other protection fiber or channel and associated connecting equipment present there between can be deactivated.
With the sharing of a protection fiber or channel on spans interconnecting common nodes, the present invention advantageously provides substantial fiber capacity savings by eliminating the need for multiple protection paths and associated connecting equipment on these spans. According to the invention, the protection fibers and associated equipment deactivated can be removed or alternatively re-provisioned to provide a cost-effective and efficient allocation of the protection resources available in the network.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.